This application makes reference to, incorporates the same herein, and claims all benefits accruing under 35 U.S.C. xc2xa7119 from an application entitled Base Station Transceiver for FH/CDMA System earlier filed in the Korean Industrial Property Office on Dec. 29, 1997, and there duly assigned Ser. No. 97-76013, a copy of which is annexed hereto.
1. Technical Field
The present invention relates to a frequency hopping/code division multiple access (FH/CDMA) system and, more particularly to a base station transceiver for a frequency hopping/code division multiple access system, which employs a junction coupling method utilizing digital switches and bandpass filters.
2. Related Art
A code division multiple access (CDMA) scheme is one of multiple access schemes proposed so that a plurality of radio stations can simultaneously make radio communication between them in the same frequency band. A frequency division multiple access (FDMA) scheme and a time division multiple access (TDMA) scheme are other schemes. The code division multiple access scheme is advantageous over the frequency division multiple access scheme and is also advantageous over the time division multiple access scheme in that the code division multiple access scheme exhibits higher efficiency of frequency utilization and can accommodate more users.
In the code division multiple access scheme, the multiple access is made by means of spread spectrum communication in which, prior to transmission of an information signal, the spectrum of the information signal is spread over a band sufficiently wide as compared to the original bandwidth of the information signal. A direct spread scheme refers to a scheme in which an information signal is directly multiplied by a spreading code in a spreading process. A frequency hopping scheme refers to a scheme in which a carrier frequency of a signal modulated by information is changed over in a discrete mode within a given frequency band. A hybrid code division multiple access scheme refers to a code division multiple access scheme in which the direct spread scheme and the frequency hopping scheme are combined.
A packet is a block of data used for transmission in packet switched systems. Data becomes packetized when it is divided up into blocks of data or packets of data. Thus, packetized data is data which is divided up into blocks of data for transmission in a packet switching network. The phrase code division multiple access (CDMA) refers to a scheme which uses a spread spectrum technique that codes each digital packet and allows multiple telephone calls to be placed on one channel, boosting caller capacity 20 times, or more, over that of an analog network. The phrase frequency hopping refers to a wireless modulation method that rapidly changes the center frequency of a transmission.
A first original signal is said to be modulated when the amplitude, frequency, or phase of the first original signal is varied in accordance with a second signal. A process of demodulation occurs when the first original signal is recovered after having been modulated.
The phrase time division multiplexing (TDM) refers to a technology that transmits multiple signals simultaneously over a single transmission path. In time division multiplexing, each lower-speed signal is time sliced into one high-speed transmission. For example, two incoming 1000 bits per second (bps) signals can be interleaved into one 2000 bits per second signal. If the two incoming signals are represented by the symbols X and Y respectively, then the interleaved signal may appear as a single stream of data as follows: XXYYXXYYXXYYXXYY. The receiving end divides the single stream back into the two original signals.
In cellular radio systems, the quality of a radio channel varies as a function of time and place. On many occasions, a transmitting antenna and a receiving antenna are not within sight of each other due to obstacles formed by terrain or buildings in the line of sight, and thus the signal detected at the receiver is a sum of beams that have traveled different paths and have been reflected from obstacles and that are, further, with different phases. The sum of several signals with different phases follows the Rayleigh distribution in cases of randomly distributed phases.
Signal fading is, furthermore, dependent on the frequency of the signal. Thus, if a frequency difference between two signals is great enough, their fadings do not correlate. A difference of 1 megahertz (MHz), for example, is large enough for signal fadings to be independent of each other.
The frequency selective fading of a signal described above is one reason for the introduction of frequency-hopping technology in digital cellular radio networks. Frequency-hopping means that the transmission frequency used in a connection is changed at predetermined intervals. Due to frequency-hopping, the transmission quality can be improved especially in situations in which the terminal equipment moves very slowly, or not at all, as is often the case with, for example, hand-held phones.
Apart from the frequency diversity achieved by frequency-hopping, the method is also advantageous in distributing the interference caused by the radio connection onto several frequencies, in which case momentary interference on any one frequency will remain small.
In some instances, if frequency-hopping is desired in a cell served by a base station, the base station equipment must be provided with at least two complete transceiver units which contain base band sections and radio frequency sections. Each unit, as such, can form an independent base station, but to implement frequency-hopping several complete transceiver units are required in the same cell. Therefore, in some instances, the base station equipment capable of frequency-hopping can be disproportionately large in small cells in comparison with the capacity needed, and the implementation of frequency-hopping can thus require heavy investments.
I have found that a communications base station transceiver has the disadvantages of high power consumption, heavy weight, and large size. Efforts have been made to improve communication systems and methods.
Exemplars of recent efforts in the art include U.S. Pat. No. 5,802,110 for Wireless Mobile System issued to Watanabe et al., U.S. Pat. No. 5,719,857 for Method and Apparatus for Implementing Frequency-hopping in a Base Station issued to Heikkinen, U.S. Pat. No. 5,657,343 for Frequency Hopping Code Division Multiple Access System and Method issued to Schilling, U.S. Pat. No. 5,570,352 for Digital Cellular Network/system with Mobile Stations Communicating with Base Stations Using Frequency-hopping and Having Enhanced Effect of Interference Diversity issued to Pxc3x6yhxc3x6nen, U.S. Pat. No. 5,459,759 for Frequency Hopping Code Division Multiple Access System and Method issued to Schilling, and U.S. Pat. No. 4,829,540 for Secure Communication System for Multiple Remote Units issued to Waggener, Sr. et al.
While these recent efforts provide advantages, I note that they fail to adequately provide a method for efficiently and conveniently providing a small and lightweight base station transceiver for a frequency hopping/code division multiple access communication system.
It is therefore an object of the present invention to provide a small and lightweight base station transceiver with a junction coupler utilizing digital switches and bandpass filters.
It is another object of the present invention to provide a small and lightweight base station transceiver including a plurality of low-powered time division duplexing (TDD) switches instead of a single high-powered time division duplexing switch.
To achieve the above objects, the present invention provides a base station transceiver for a frequency hopping/code division multiple access system including N forward pre-processors for scrambling Bose-Chaudhuri-Hocquenghem (BCH) encoded control/signaling data and interleaved traffic data, packetizing the scrambled data, and generating hopping frequency control data; a forward signal switch for switching signals output from the forward pre-processors; N forward post-processors for lowpass-filtering signals output from the forward signal switch, frequency-modulating the lowpass-filtered signals with a transmission frequency synthesizing signal, and filtering and amplifying the frequency-modulated signals at a transmission frequency band; a transmission/reception selector for selecting a transmission or reception path; N reverse pre-processors for demodulating received signals selected by the transmission/reception selector with a reception frequency synthesizing signal to restore clock and data, and detecting a received signal strength indication signal; a reverse signal switch for switching signals output from the reverse pre-processors; N reverse post-processors for measuring signal-to-noise ratios of signals output from the reverse signal switch, and de-packetizing and descrambling the signals output from the reverse signal switch to divide the signals into the traffic data and the control/signaling signal; and a time division duplexing timing controller for generating a time division duplexing timing control signal for controlling the transmission/reception selector.
To achieve these and other objects in accordance with the principles of the present invention, as embodied and broadly described, the present invention provides an apparatus, comprising: a plurality of first preprocessing units receiving and then scrambling first control data, signal data, and traffic data, packetizing the scrambled data to divide the scrambled data into packets, generating frequency control data controlling hopping frequencies, and outputting said packetized data and said frequency control data; a first signal switch switching said packetized data and said frequency control data output from said plurality of first preprocessing units, and outputting primary signals corresponding to said switched data; a plurality of first postprocessing units lowpass-filtering said primary signals output from said first signal switch, frequency modulating said lowpass-filtered signals with a secondary signal synthesizing transmission frequency, and filtering and amplifying said frequency modulated signals at a transmission frequency band; a selection unit selecting a path from among a transmission path and a reception path; a plurality of second preprocessing units demodulating received signals selected by said selection unit with a tertiary signal synthesizing reception frequency to restore clock and data, and detecting a received signal strength indication signal; a second signal switch switching signals output from said plurality of second preprocessing units; a plurality of second postprocessing units measuring signal-to-noise ratios of signals output from said second signal switch, and de-packetizing and unscrambling said signals output from said second signal switch to divide said signals into said first control data, said signal data, and said traffic data; and a control unit being coupled to said selection unit and generating a timing control signal utilizing time division duplexing to control said selection unit, wherein said apparatus corresponds to a base station transceiver for a frequency hopping code division multiple access system.
To achieve these and other objects in accordance with the principles of the present invention, as embodied and broadly described, the present invention provides an apparatus, comprising: a plurality of N forward preprocessors respectively processing transmission signals of a plurality of N channels, wherein the symbol N represents a number corresponding to a quantity; a forward signal switch switching said transmission signals to unused channels; a plurality of N forward postprocessors processing output signals of said forward signal switch; a plurality of N time division duplexing switches being switchable to a path selected from among a forward signal path and a reverse signal path according to a timing control signal utilizing time division duplexing, said N time division duplexing switches respectively receiving said processed signals output from said N forward postprocessors; a timing controller generating said timing control signal; a plurality of N bandpass filters bandpass-filtering output signals of said time division duplexing switches; a junction coupler coupling output signals of said bandpass filters; first and second antennas transmitting coupled signals output from said junction coupler, and receiving radio signals; said bandpass filters bandpass-filtering said radio signals received through said first and second antennas; said time division duplexing switches switching said radio signals to the reverse signal path according to said timing control signal; a plurality of N reverse preprocessors processing output signals of said time division duplexing switches; a reverse signal switch switching the processed signals output from said reverse s preprocessors to unused channels; a plurality of N reverse postprocessors processing the switched signals output from said reverse signal switch, wherein said apparatus corresponds to a base station transceiver for a frequency hopping code division multiple access system.
To achieve these and other objects in accordance with the principles of the present invention, as embodied and broadly described, the present invention provides a method, comprising: receiving and then scrambling first control data, signal data, and traffic data, packetizing the scrambled data to divide the scrambled data into packets, generating frequency control data controlling hopping frequencies, and outputting said packetized data and said frequency control data; switching said packetized data and said frequency control data, and outputting primary signals corresponding to said switched data, said switching of said packetized data and said frequency control data being performed by a first signal switch; lowpass-filtering said primary signals, frequency modulating said lowpass-filtered signals with a secondary signal synthesizing transmission frequency, and filtering and amplifying said frequency modulated signals at a transmission frequency band; selecting a path from among a transmission path and a reception path, said selecting being performed by a plurality of special switches; demodulating received signals when the reception path is selected, said demodulating being performed with a tertiary signal synthesizing reception frequency to restore clock and data, and detecting a received signal strength indication signal; switching demodulated received signals and outputting switched signals, said switching of said demodulated received signals being performed by a second signal switch; measuring signal-to-noise ratios of said switched signals, and de-packetizing and unscrambling said switched signals to divide said signals into said s first control data, said signal data, and said traffic data; and generating a timing control signal utilizing time division duplexing to control said selecting of said path by said plurality of special switches, wherein said method corresponds to operations of a base station transceiver for a frequency hopping code division multiple access system.
The present invention is more specifically described in the following paragraphs by reference to the drawings attached only by way of example. Other advantages and features will become apparent from the following description and from the claims.